example, there may be a perception that a given organism is dependent on aquatic vegetation 
when in fact it is more of a case of co-occurrence between the organism and the vegetation that 
share similar physical requirements, rather than a dependence of the organisms on conditions 
provided by the vegetation. An example would be migratory fishes, such as Pacific salmonids. 
The level to which these fishes utilize estuarine habitat in their migratory cycle is not well 
known, and the utilization of estuarine seagrass beds is thought to vary greatly among salmonid 
species and stocks. If such vegetation were not present, would salmon simply reduce their 
residence time in the estuary and continue their seaward migration sooner than they would 
otherwise? It must also be assessed whether the organism is associated with the vegetated 
habitat throughout its life, or only occupies the habitat during specific life history phases or 
seasons. It should be noted that many species have life history stages that are notoriously 
difficult to observe or sample, and it may be difficult to establish whether and how much these 
organisms are truly dependent on aquatic vegetation. 
Characterization of the Species (Assessment Endpoint)-Habitat Relationships 
In order to quantify species-habitat relationships, it is necessary to define the structural and 
functional attributes of aquatic vegetation that are to be documented and their alignment with the 
hypothesized assessment endpoint requirements. Standardization is necessary to ensure that data 
are collected in an agreed upon and consistent manner among the research efforts. There must 
also be agreement and coordination among broader research groups: aquatic vegetation is 
considered in this document from the perspective of its function as a habitat, but other research 
will be evaluating the effect of nutrient loading and other anthropogenic stressors on aquatic 
vegetation, and so the data collected for habitat and nutrient work (e.g., see Section 5) should 
support one another. Examples of vegetation attributes include species composition, areal extent, 
fragmentation or patchiness of the habitat, zonation, productivity, density, growth rates, condition 
(or other evaluations of the vegetation's "health"), degree of protection from predators the 
vegetation might afford, substrate characteristics, water quality, seasonal alterations to the 
habitat, and whether it directly provides food for an assessment endpoint or food for a secondary 
endpoint such as forage organisms. Standardization of data is highly desirable, but it must not 
neglect regional differences in vegetated habitat. For example, many marine vegetated habitats 
are spatially extensive and largely monotypic, and efforts to characterize habitats may focus 
largely on vegetation condition and extent. In contrast, vegetated habitat of Great Lakes coastal 
wetlands is diverse and variable over relatively small spatial scales, so that research efforts here 
will focus on distribution and interspersion of habitat types with the ultimate goal of deriving 
habitat evaluation procedures capable of synthesizing habitat components across entire wetlands. 
Quantifying the Consequences of Alteration of Vegetated Aquatic Habitats 
After identifying important species that depend in some way on aquatic vegetation, and having 
defined the suite of vegetation attributes relevant to those organisms, the research will then 
quantify the relationships between the two. Quantifying species-vegetated habitat relationships 
in sufficient detail to permit evaluation of both catastrophic and incremental habitat alteration 
requires developing mechanistic or empirical relationships spanning a range of habitat extent and 
characteristics. Insofar as possible, research also should identify key portions of the response 
relationships including response thresholds, maximum biological potential, and levels above 
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